Residual fuel oil additive

ABSTRACT

Fuel additives are disclosed for high-asphaltene carbonaceous fuels such as residual fuel oil or coal. Such additives provide improved combustion characteristics. Such improved combustion characteristics include one or both of improved efficiency and decreased emissions of pollutants. In particular, the fuel additives include an extract from a plant such as fescue, alfeque, or alfalfa, and optionally, an organometallic compound. The use of a fuel additive including both a plant extract and an organometallic compound is particularly useful in improving the combustion characteristics of fuels with particularly high asphaltene content.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Provisional Application No. 60/753,318, filed Dec. 21, 2005, the entire disclosure of which is incorporated by reference.

TECHNICAL FIELD

The invention pertains to fuel additives for carbonaceous fuels having high asphaltene content such as residual fuel oil and coal. Benefits from the use of such fuel additives may include one or more of reduced particulate matter emissions, reduced nitrogen oxide emissions, and improved combustion efficiency.

BACKGROUND OF THE INVENTION

Carbonaceous fuels with high asphaltene content such as residual fuel oil and coal tend to liberate large amounts of energy on combustion, and therefore, find utility in applications where a low cost, high energy fuel is desired. However, such high-asphaltene carbonaceous fuels generally burn with less efficiency than other hydrocarbon fuels, and may often contain quantities of undesirable compounds that limit combustion and result in elevated levels of pollutants.

Residual fuel oils (also referred to as “resid” or “resid fuel”) are generally the low grade products that remains after the distillation of lighter petroleum products which may include gasoline, jet fuel, diesel fuel, No. 4 fuel oil, and No. 5 light or heavy fuel oil. Examples of residual fuel oils include No. 6 fuel oil and Bunker C fuel oil.

The compounds referred to as “asphaltenes” generally include polynuclear aromatics and/or polycyclic materials. While certain parts of the world such as North America tend to have specifications which limit the amount of asphaltenes in fuels such as residual fuel oils, such fuels still have relatively high levels of asphaltenes compared to other, lighter hydrocarbon fuels. For example, in the United States, specifications limit the asphaltene content of residual fuel oil to less than about 8 wt. %. However, in other parts of the world, asphaltene specifications tend to be either non-existent, or significantly higher than those in North America. Therefore, residual fuel oils in other parts of the world may have asphaltene contents of 10 wt. % or higher. As a fairly heavy carbonaceous fuel, coal also tends to have high concentrations of ring structures which may include anthracene and phenanthrene which for purposes of this specification are to be included as “asphaltenes.” It should be noted that as coal becomes “older,” more of such rings form and become interconnected such that coal can also be considered a high-asphaltene carbonaceous fuel. For purposes of this specification, the term “high-asphaltene carbonaceous fuel” is intended to broadly encompass carbonaceous fuels which have asphaltene content of at least 4 wt %.

Examples of the pollutants that can result from the combustion of high-asphaltene carbonaceous fuels include ozone, particulate matter (PM), carbon monoxide, nitrogen oxides (NO_(x)), sulfur dioxide, polynuclear aromatic compounds, and soluble organic fractions. In the United States, numerous state and national agencies have or are adopting ambient air quality standards which may require reduced emissions from the combustion of high-asphaltene carbonaceous fuels. Among the users of resid oils are power plants and ocean-going ships. In Southern California, for example, emissions from ships entering the port of Los Angeles are considered to be a major cause of regional air pollution.

Considerable effort has been expended by petroleum refiners to formulate fuels that reduce emissions. The most common approach to formulating compliant fuels involves adjusting refinery processes so as to produce a fuel meeting the specifications set forth by appropriate government agencies. However, such an approach is difficult for residual fuels, and the drawbacks to such an approach include high costs in reconfiguring refinery processes, and possible negative effects on the quantity or quality of other refinery products.

SUMMARY OF THE INVENTION

Embodiments of the present invention include systems, methods, and compositions which may provide improved combustion characteristics of high-asphaltene carbonaceous fuels. Examples of the combustion characteristics which may be improved by embodiments of the invention include one or both of increased combustion efficiency, and reduced pollutant discharge. Examples of the pollutants which may be reduced include one or more of ozone, particulate matter (PM), carbon monoxide, nitrogen oxides (NO_(x)), sulfur dioxide, polynuclear aromatic compounds, and soluble organic fractions.

In some embodiments, a fuel additive is provided comprising a plant extract. In this specification, the term “plant extract” is intended to broadly encompass extracts of all types of plants, excluding the roots and bark, and even includes plants such as algae. Suitable plant extracts are extracts from green and other colored plants as such plants tend to have high concentrations of desirable extracts. However, even white and light colored plants include such extracts, though at lower concentrations. Particularly suitable extracts are from green and other dark leafy plants such as those from the Leguminosae family which includes fescue, alfeque, and alfalfa.

In a preferred embodiment, the plant extract is combined with an organometallic material. The inclusion of an organometallic compound is especially useful for treating fuels having particularly high asphaltene contents in the range of 8 wt. % or higher. Examples of organometallic materials are hydrocarbon-soluble organometallic compounds that include a metal selected from the first and second row transition metals. One metal of particular interest is iron, and particularly suitable organometallic materials include iron pentacarbonyl, iron naphthenate, ferrocene, and combinations. The fuel additive may optionally include an oil-soluble carrier. Examples of suitable oil-soluble carriers include hydrocarbons such as toluene, aromatic blends, naphthas, gasoline, diesel fuel, jet fuel, and mixtures thereof. In one embodiment, the oil soluble carrier is non-oxygenated.

In certain embodiments, the fuel additive may include other optional ingredients. Such optional ingredients may include one or more of an oxygen carrier, a stability aid, a lubricity aid, an anti-oxidant, and a combustion improver. Meadowfoam oil may be used as a stability aid, an anti-oxidant, and a lubricity aid. Suitable oxygen carriers include carotenoids. Examples of antioxidants include 1,2-dihydroquinolines, and in particular, 2,2,4-trimethyl-6-ethoxy-1,2-dihydroquinoline. Examples of combustion improvers include compounds known as cetane improvers or ignition accelerators. Examples of combustion improvers include alkyl nitrates such as 2-ethylhexyl nitrate.

In another embodiment of the present invention, a method for improving the combustion characteristics of a high-asphaltene carbonaceous fuel comprises adding a fuel additive as described above to a high-asphaltene carbonaceous fuel prior to or during combustion.

In another embodiment of the present invention, an additized high-asphaltene carbonaceous fuel is provided which comprises a high-asphaltene carbonaceous fuel and a fuel additive as described above.

In still another embodiment of the invention, a method for preparing a fuel additive comprises mixing a plant extract with an oil-soluble carrier and one or more of an organometallic material, an oxygen carrier, a stability aid, a lubricity aid, an anti-oxidant, and a combustion improver. In another embodiment of the invention, the fuel additive is prepared in an oxygen-free or reduced-oxygen atmosphere, and optionally may include the step of excluding sources of UV radiation during the preparation. In still another embodiment, non-oxidized oil-soluble carriers and non-oxidized oxygen carriers are used.

The plant extract used in various embodiments of the invention may be obtained by solvent extraction from whole plants using hydrocarbon-soluble solvents. Polar or nonpolar hydrocarbon-soluble solvents may be used for the extraction. The extract resulting from the extraction process is a crude material containing over 300 individual compounds. In one embodiment, the extract has a paste- or mud-like consistency that may be described as a solid or semi-solid, rather than a liquid. Such extracts typically contain chlorophyll A and chlorophyll B with a higher concentration of chlorophyll A over chlorophyll B. The color of such an extract is generally a deep black-green with some degree of fluorescence. Such an extract may be recovered from most plants though green and darker leafy plants tend to have higher concentrations. Extracts from plants from the Leguminosae family are suitable. While such a solid or semi-solid form is generally considered to be preferred for most embodiments, in other embodiments, a liquid or other form may be suitable, and may even be preferred. Furthermore, synthetic materials, for example synthetic carotenoids, chlorophylls, or xanthopylls, may be used instead of or in addition to natural plant extracts.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a plot of NO_(x) emissions measured at the furnace exit for the various fuel additives used in the EERC Test;

FIG. 2 is a plot of NO_(x) emissions measured at the baghouse for the various fuel additives used in the EERC Test;

FIG. 3 is a plot of dust loading for the EERC Test;

FIG. 4 is a plot of heat flux divided by fuel firing rate versus excess air for the EERC Test; and

FIG. 5 is a plot of feed rate versus temperature for the EERC Test.

DETAILED DESCRIPTION

As used in this specification, the term “β-carotene mixture” is defined as a mixture of from about 89 to about 98% trans β-carotene with the remainder being from about 2 to 11% of various cis β-carotene isomers or other poly-unsaturated conjugated hydrocarbons. An example of such a β-carotene mixture is ISOMIXTENE®, a product sold by DSM Nutritional Products, Inc. of Parsippany, N.J.

Embodiments of the present invention are directed to systems, methods, and compositions which improve the combustion characteristics of high-asphaltene carbonaceous fuels. Examples of the combustion characteristics which may be improved include increased combustion efficiency, and reduced emissions of one or more pollutants such as ozone, particulate matter (PM), carbon monoxide, nitrogen oxides (NO_(x)), sulfur dioxide, polynuclear aromatic compounds, and soluble organic fractions.

In one embodiment, a fuel additive comprises a plant extract. Suitable plant extracts include extracts from green leafy plant material. Particularly useful plant extracts are extracts from plants of the Leguminosae family which may include fescue extract, alfeque extract, alfalfa extract, and combinations thereof. The plant extract may be provided in an amount such that the high-asphaltene carbonaceous fuel to be treated includes a plant extract concentration by weight in the range of about 0.5 ppm to about 10,000 ppm, preferably from about 200 ppm to about 2000 ppm, and more preferably at about 800 ppm. Without being bound by theory, it is believed that the oxygen-gathering properties of such plant extracts provide the beneficial improvements to the combustion of high-asphaltene carbonaceous fuels such as residual fuel oil and coal.

The plant extracts may be obtained using extraction methods well known to those of skill in the art. Solvent extraction methods using polar or nonpolar hydrocarbon-soluble solvents are generally preferred. Any suitable extraction solvent may be used which is capable of separating the suitable fractions from the plant material. Suitable nonpolar solvents include cyclic, straight chain, and branched-chain alkanes containing from about 5 or fewer to 12 or more carbon atoms. Specific examples of acyclic alkane solvents include pentane, hexane, heptane, octane, nonane, decane, mixed hexanes, mixed heptanes, mixed octanes, isooctane, and the like. Examples of cycloalkane solvents include cyclopentane, cyclohexane, cycloheptane, cyclooctane, methylcyclohexane, and the like. Alkenes such as hexenes, heptenes, octenes, nonenes, and decenes are also suitable for use, as are aromatic hydrocarbons such as benzene, toluene, and xylene. Halogenated hydrocarbons such as chlorobenzene, dichlorobenzene, trichlorobenzene, methylene chloride, chloroform, carbon tetrachloride, perchloroethylene, trichloroethylene, trichloroethane, and trichlorotrifluoroethane may also be used. Generally preferred nonpolar solvents are C₆ to C₁₂ alkanes, particularly n-hexane.

Suitable polar solvents may include, but are not limited to, acetone, methyl ethyl ketone, other ketones, methanol, ethanol, other alcohols, tetrahydrofuran, methylene chloride, chloroform, or any other suitable polar solvent.

Hexane extraction is a commonly used technique for extracting oil from plant material. It is a highly efficient extraction method that extracts virtually all oil-soluble fractions from the plant material. In a typical hexane extraction, the plant material is comminuted. Grasses and leafy plants may be chopped into small pieces while seeds are typically ground or flaked. The plant material may be pelletized to pellets of ±½ to ¾ inch. The plant material is typically exposed to hexane at an elevated temperature. The hexane, a highly flammable, colorless, volatile solvent that dissolves out the oil, typically leaves only a few weight percent of the oil in the residual plant material. The oil and solvent mixture may be heated to about or above 100° C. to remove most of the hexane, and may then be distilled to remove all traces of hexane. Alternatively, hexane may be removed by evaporation at reduced pressure. The resulting plant extract is suitable for use in producing the fuel additives of the present invention.

Other extraction processes include supercritical fluid extraction, typically with carbon dioxide, but other gases such as helium, argon, xenon, and nitrogen may also be used as solvents in supercritical fluid extraction methods.

Still another useful extraction process is mechanical pressing, also known as expeller pressing, which removes oil through the use of continuously driven screws that crush the seed or other oil-bearing material into a pulp from which the oil is expressed. Friction created in the process can generate temperatures between about 50° C. and 90° C., or external heat may be supplied. Cold pressing generally refers to mechanical pressing conducted at a temperature of 40° C. or less with no external heat applied. The yield of oil extract that may be obtained from a plant material may depend upon any number of factors, but primarily upon the oil content of the plant material. For example, a typical oil content of vetch (hexane extraction, dry basis) is approximately 4 to 5 wt. %, while that for barley is approximately 6 to 7.5 wt. %, and that for alfalfa is approximately 2 to 4.2 wt. %.

Plant oil extracts for use in edible items or cosmetics typically undergo additional processing steps to remove impurities that may affect the appearance, shelf life, taste, and the like, to yield a more refined product. The impurities include may include phospholipids, mucilaginous gums, free fatty acids, color pigments and fine plant particles. Different methods are used to remove these by-products including water precipitation or precipitation with aqueous solutions of organic acids. Color compounds are typically removed by bleaching, wherein the oil is typically passed through an absorbent such as diatomaceous clay. Deodorization may also be conducted, which typically involves the use of steam distillation. While the extracts used as fuel additives in the present invention may include such additional processing steps, such additional steps are generally unnecessary.

The fuel additive may optionally include an organometallic compound. Suitable organometallic compounds are hydrocarbon-soluble organometallic compounds that include a metal selected from the first and second row transition metals particularly suitable organometallic compounds include iron pentacarbonyl, iron naphthenate, ferrocene, and combinations. The inclusion of an organometallic compound is believed to be particularly useful in improving the combustion characteristics of fuels with particularly high asphaltene content such as residual fuel oils used in areas of the world other than North America. The organometallic compound may be provided in an amount such that the fuel to be treated includes a concentration by weight of organometallic compound in the range of about 0.5 ppm to about 10,000 ppm as metal, preferably from about 200 ppm to about 2000 ppm as metal, and more preferably at about 800 ppm as metal. Without being bound by theory, it is believed that the inclusion of an organometallic compound provides a catalytic effect to the reactions promoted by the plant extract material.

The fuel additive may further comprise meadowfoam oil. Meadowfoam oil has a number of useful properties, and can function as an oxygen carrier, a stability aid, and an anti-oxidant. Because the plant extracts used in the fuel additives of the present invention have oxygen-gathering properties, and therefore, can be unstable, the inclusion of a material such as meadowfoam oil can help to maintaining the stability of the plant extracts and prevent their oxidation.

The composition may further optionally include at least one carotene which may be provided in the form of a β-carotene mixture such as ISOMIXTENE®. Although carotenoids such as β-carotene mixtures are disclosed, other molecules having extended pi or double bonded structures of from about 2 to 11 or more conjugated double bonds are also believed to similarly provide improved combustion characteristics for resid or other hydrocarbon fuels when used as additives for such fuels. The moieties of such molecules including the double bond structures can be terminated by at least one end group further comprising an aromatic, cyclic, or branched 5 to 8 carbon moiety that is saturated or unsaturated. Examples include cyclo-pentane, cyclo-pentene, cyclo-hexane, cyclo-hexene, cyclo-heptane, cyclo-heptene, isopentane or isopentene. Aromatic structures are considered as extended pi structures also. The unsaturated/aromatic portions and the end groups can additionally include various other substituents such as hydroxyl groups, keto groups, alkyl groups, alkenyl groups and combinations. Additionally, the additive molecules can comprise from 12 to about 40 or 50 carbon atoms. Such molecules are found in mixtures of synthetic carotene precursors. Such additives may be obtained from natural or synthetic sources.

Furthermore, lycopene is another example of a suitable carotene. Other suitable carotenoids and carotene precursors are disclosed in German patent 954,247, issued in 1956 and incorporated by reference.

If the fuel additive comprises a carotene, it may further comprise an antioxidant. Suitable antioxidants include alkyl phenols such as 2-tert-butylphenol, 2,6-di-tert-butylphenol, 2-tert-butyl-4-n-butylphenol-, 2,4,6-tri-tert-butylphenol, 2,6-di-tert-butyl-4-n-butylphenol, and mixtures thereof. Such antioxidants are suited for use as stabilizers for middle distillate fuels. Other antioxidants include hindered phenolic antioxidants such as 2,6-di-t-butyl-4-methylphenol; 2,6-di-t-butylphenol; 2,2′-methylene-bis(6-t-butyl-4-methylphenol); n-octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate; 1,1,3-tris(3-t-butyl-6-methyl-4-hydroxyphenyl) butane; pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate]; di-n-octadecyl(3,5-di-t-butyl-4-hydroxybenzyl)phosphonate; 2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl) mesitylene; tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, pentaeryfritol co-esters derived from pentaerythritol, (3-alkyl-4-hydroxyphenyl)-alkanoic acids and alkylthioalkanoic acids or lower alkyl esters of such acids, and combinations thereof. Such stabilizers are useful with organic material normally susceptible to oxidative and/or thermal deterioration. Also useful are the reaction product of malonic acid, dodecyl aldehyde and tallowamine, hindered phenyl phosphates, hindered piperidine carboxylic acids and metal salts thereof; acylated derivatives of 2,6-dihydroxy-9-azabicyclo[3.3.1]nonane; bicyclic hindered amines; sulfur containing derivatives of dialkyl-4-hydroxyphenyltriazine, bicyclic hindered amino acids and metal salts thereof, trialkyl substituted hydroxybenzyl malonates, hindered piperidine carboxylic acids and metal salts thereof, pyrrolidine dicarboxylic acids and esters, metal salts of N,N-disubstituted beta.-alanines, hydrocarbyl thioalkylene phosphates, hydroxybenzyl thioalkylene phosphates, and the like.

Specific antioxidants useful in the present invention are the quinoline or hydro quinoline compounds such as 1,2 dihydro quinoline compounds. More particularly, 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline, commonly referred to as ethoxyquin, may be used as an antioxidant. Ethoxyquin is sold under the trademark SANTOQUIN® by Novus International Inc. of St. Louis, Mo., and is widely used as an antioxidant for animal feed and forage.

The fuel additives of the present invention may also contain a combustion improver such as a cetane improver or ignition accelerator. Suitable combustion improvers are organic nitrate materials. Preferred organic nitrates are substituted or unsubstituted alkyl or cycloalkyl nitrates having up to about 10 carbon atoms, and preferably from 2 to 10 carbon atoms. The alkyl group can be either linear or branched. Specific examples of suitable nitrate compounds include methyl nitrate, ethyl nitrate, n-propyl nitrate, isopropyl nitrate, allyl nitrate, n-butyl nitrate, isobutyl nitrate, sec-butyl nitrate, tert-butyl nitrate, n-amyl nitrate, isoamyl nitrate, 2-amyl nitrate, 3-amyl nitrate, tert-amyl nitrate, n-hexyl nitrate, 2-ethylhexyl nitrate, n-heptyl nitrate, sec-heptyl nitrate, n-octyl nitrate, sec-octyl nitrate, n-nonyl nitrate, n-decyl nitrate, n-dodecyl nitrate, cyclopentylnitrate, cyclohexylnitrate, methylcyclohexyl nitrate, isopropylcyclohexyl nitrate, and the esters of alkoxy substituted aliphatic alcohols, such as 1-methoxypropyl-2-nitrate, 1-ethoxpropyl-2 nitrate, 1-isopropoxy-butyl nitrate, 1-ethoxylbutyl nitrate and the like. Preferred alkyl nitrates are ethyl nitrate, propyl nitrate, amyl nitrates, and hexyl nitrates. Other preferred alkyl nitrates are mixtures of primary amyl nitrates or primary hexyl nitrates. By “primary” it is meant that the nitrate functional group is attached to a CH₂ group of the amyl or hexyl group. Examples of primary hexyl nitrates include n-hexyl nitrate, 2-ethylhexyl nitrate, 4-methyl-n-pentyl nitrate, and the like. Preparation of the nitrate esters can be accomplished by any of the commonly used methods, such as by esterification of the appropriate alcohol, or reaction of a suitable alkyl halide with silver nitrate. These additives can be present the same or different amounts as the other components of the fuel additive

The fuel additives may further include a diluent or solvent carrier. Such a carrier is useful because, in general, low concentrations of the particular components of the fuel additive are effective in achieving desirable results, and therefore, the use of a carrier simplifies the addition of the fuel additive. The use of a carrier can further help to maintain the components in solution, and can help to prevent oxidation of the components.

Suitable solvents for use as the carrier include one or more of an aromatic hydrocarbon such as toluene or xylene, or other hydrocarbons such as gasoline, jet fuel, or diesel fuel. In one embodiment, a mixed aromatic solvent comprising various xylene isomers is used. Examples of such solvents include those commercially available in North America from ExxonMobil Chemical and sold under the names AROMATIC 100 FLUID and AROMATIC 150 FLUID. In one embodiment, a mixture of AROMATIC 100 FLUID AND AROMATIC 150 FLUID is used.

When blending the particular components of the fuel additive, it may be useful to prepare the fuel additive in an oxygen free or low oxygen atmosphere to prevent oxidation of the fuel additive components. Optionally, the components may be blended under conditions in which sources of UV radiation are excluded to further prevent degradation of the components.

In those embodiments where the fuel additive includes a plant extract such as fescue extract, alfeque extract, or alfalfa extract, meadowfoam oil, and a carotene, the weight ratio of plant extract to carotene may be from about 50:1 to about 20:1, and preferably is from about 24:1 to about 10:1. The ratio of grams of plant extract to milliliters of meadowfoam oil may be from about 12:1 to about 20:1, and preferably is from about 6:1 to about 10:1. The ratio of milliliters meadowfoam oil to grams of carotene may be from about 12:1 to about 20:1, and preferably is from about 6:1 to about 1:1.

In those embodiments where the fuel additive includes a carotene and an antioxidant, the ratio of carotene to antioxidant may be from about 20:1 to about 1:1, preferably is from about 15:1 to about 5:1, and more preferably is about 10:1.

In another embodiment of the invention, where the fuel additive includes plant extract and meadowfoam oil, the two may be provided in a weight ratio from about 1:100 to about 100:1. In an embodiment of the invention, the concentration of plant extract in the total fuel additive composition may be from about 0.06 weight % to about 6 weight %, and preferably is from about 0.12 weight % to about 3 weight %. The concentration of meadowfoam oil may range from about 0.05 weight % to about 5 weight % of the total fuel additive composition, and preferably is about 0.5 weight % of the total fuel additive composition.

Such fuel additives may be blended into high-asphaltene carbonaceous fuels such that the plant extract and organometallic material are present in the fuel in the concentrations set forth above.

In embodiments in which the fuel additive includes a plant extract, a non-oxidized carotene, an antioxidant, and meadowfoam oil, certain factors may be useful in determining appropriate ratios for the components. Such factors may include the elevation at which the fuel is to be combusted, the type of engine or device using the fuel, and the particular fuel properties. Examples of different types of engines or devices include two-cycle diesel engines and stationary boilers. Examples of relevant fuel properties include sulfur content, mercaptan content, olefin content, aromatic content and asphaltene content. For example, if a fuel has a high sulfur content of 1 wt. % or more, or a high aromatics content of 25 wt. % or more, the ratios may be adjusted such as to provide additional plant extract or additional non-oxidized carotene.

According to another embodiment of the invention, an additized fuel is provided in which a fuel additive as set forth above is blended with a high-asphaltene carbonaceous fuel. Formulated fuel compositions according to embodiments of the invention can further contain other known additives such as detergents, antioxidants, demulsifiers, corrosion inhibitors, metal deactivators, diluents, cold flow improvers, and thermal stabilizers.

According to another embodiment of the invention, a method for improving combustion characteristics of a high-asphaltene carbonaceous fuel comprises the step of adding such a fuel additive to a high-asphaltene carbonaceous fuel prior to or during combustion.

Fuel additives of the present invention may be introduced into residual fuel oil in a number of different ways. For example, the residual fuel oil to be combusted may be pre-mixed to include the fuel additive. In another example, the fuel additive is injected into a residual fuel oil stream being fed to a burner or other combustion device. In such an embodiment, the fuel additive may be injected using a metered injection system. Such a metered injection system may optionally be controlled by a computer system that can optimize the flow of any or all of the components to the combustion device to optimize its operation.

For coal, such fuel additives can similarly be added in a number of different ways. For example, the fuel additive may be sprayed over the coal prior to combustion. Alternatively, the fuel additive may be pumped or sprayed into the coal burner along with the coal using a metered injection system as described above.

EERC Laboratory Testing

Test runs were conducted at the EERC Laboratory in Grand Forks, N. Dak. Six drums of residual fuel oil were used in the tests. The residual fuel oil was supplied by Sun Coast Resources in Houston, Tex. The properties of the residual fuel oil used are set forth in Table 1. It has a moderate sulfur content of about 2.63%, with a very high heating value of 44.5 MJ/kg at a moisture content of 2.40%. The Karl Fischer water content was determined to be 0.21%. The volatile content of the sample was determined to be 89.30%, with fixed carbon present at the 8.29% level. The theoretical emission limit of sulfur dioxide was determined to be 1714 ppm at a flue gas oxygen concentration of 2.0%. This equates to a 1.18 kg/MJ emission rate for the sulfur dioxide (SO₂). The residual fuel oil had a specific gravity of 0.9952, and the amount of sediment was determined to be 0.05%. Table 1 also provides the proximate, ultimate, and heating value analyses for the residual fuel oil tested along with the theoretical emission limit of sulfur.

TABLE 1 As-fired Residual Fuel Oil Analyses (standard ASTM* analyses) Test Number AF-CTS-745 & 746 Fuel Description Residual Fuel Oil Sample Number 05-0165 As-Fired H₂O-free Proximate Analysis, % Moisture 2.40 — Volatile Matter 89.30 91.48 Fixed Carbon 8.29 8.51 Ash 0.01 0.01 Ultimate Analysis, % Hydrogen 10.48 10.46 Carbon 83.41 85.44 Nitrogen 0.86 0.88 Sulfur 2.63 2.69 Oxygen 2.62 0.52 Ash 0.01 0.01 Heating Value, MJ/kg 44.25 45.33 Maximum SO₂, ppm @ 3.5% O₂ 1714 g/MJ 5.74 Specific Gravity @ 60° F. 0.9952 Karl Fischer Water, % 0.21 Sediment, % 0.05 *American Society for Testing and Materials

The residual fuel oil was stored cold prior to testing. Barrel heaters were used to heat the residual fuel oil to 121° C. prior to transferring it to the feed hopper situated above the pump. A barrel heater was strapped to the tank of the feed hopper to keep the residual fuel oil hot during testing, averaging between 113° and 118° C. for use in the test periods shown here. Although the oil appeared to be rather viscous at this temperature, a homogeneous phase was maintained so that a readily controllable feed rate to the combustor was achieved for all test periods.

The test apparatus at the EERC facility includes a furnace with a capacity of approximately 19 kg/hr (845 MJ/hr) of residual fuel oil. The combustion chamber is 0.76 meters in diameter, 2.44 meters high, and refractory-lined for combustion testing of various types of fuels. The furnace diameter may be reduced to 0.66 meters to elevate the temperature entering the convective pass. Furnace exit gas temperatures (FEGTs) as high as 1400° C. have been achieved during combustion testing in this mode. However, most tests are performed using the standard configuration (0.76 meter inside diameter), with the FEGT maintained between 1100° C. and 1200° C. though the FEGT is typically raised to between 1250° C. and 1300° C. for the combustion of residual fuel oil. Two Type S thermocouples, located at the top of the combustion chamber, are used to monitor the FEGT. They are situated 180° apart at the midpoint of the transition from vertical to horizontal flow. Excess air levels are controlled manually by adjusting valves on the primary and secondary air streams. The typical distribution is 15% primary and 85% secondary to achieve a typical excess air level of 20%.

When firing liquid fuels such as residual fuel oil, a pump is used to convey the fuel through a dual-fluid atomizer into the combustion chamber. Air or steam is commonly used as the atomizing fluid. Combustion air is preheated by an electric air heater. Heated secondary air is introduced through an adjustable swirl burner. Flue gas passes out of the furnace into a 10-inch-square duct that is also refractory-lined. A vertical probe bank located in the duct is designed to simulate superheated surfaces in a commercial boiler. After leaving the probe duct, the flue gas passes through a series of water-cooled, refractory-lined heat exchangers and a series of air-cooled heat exchangers before being discharged through either an electrostatic precipitator (ESP) or a baghouse (BH) for particulate removal.

At the EERC facility, flame stability is assessed by observation of the flame and its relation to the burner quart as a function of secondary air swirl and operating conditions at full load and under turndown conditions. An International Flame Research Foundation-(IFRF)-type adjustable secondary air swirl generator uses primary and secondary air at approximately 15% and 85% of the total air, respectively, to adjust swirl between 0 and a maximum of 1.9. Swirl is defined as the ratio of the radial (tangential) momentum to axial momentum imparted to the secondary air by movable blocks internal to the burner and is used to set up an internal recirculation zone (IRZ) within the flame that allows greater mixing of combustion air and fuel. Swirl is imparted by moving blocks to set up alternate paths of radial flow and tangential flow to create a spin on the secondary air stream that increases the turbulence in the near-burner zone.

At the fully open position of the swirl block, the secondary air passes through the swirl burner unaffected, and the momentum of this stream has only an axial component such that the air enters the combustion chamber as a jet. As the angle of the blocks changes, the air begins to spin or “swirl” and the radial component of the momentum is established, creating the IRZ in the near burner region. It is the ratio of this radial component of the momentum to the axial component that establishes the quantity defined as swirl.

The adjustable-swirl burner used by the EERC during flame stability testing consists of two annular plates and two series of interlocking wedge-shaped blocks, each attached to one of the plates. The two sets of blocks can form alternate radial and tangential flow channels, such that the air flow splits into an equal number of radial and tangential streams which combine further downstream into one swirling flow. By simply rotating the movable plate, radial channels are progressively closed and tangential channels opened so that the resulting flux of angular momentum increases continuously, between zero and a maximum value. This maximum swirl setting depends on the total air flow rate and the geometry of the swirl generator. Swirl can be calculated from the dimensions of the movable blocks (the ratio of the tangential and radial openings of the blocks) or from the measurement of the velocity of the air stream (obtaining both radial and axial components).

Secondary air swirl is used to stabilize the flame. In the absence of swirl, loss of flame may result, increasing the risk of dust explosion. As swirl is applied to the combustion air, fuel droplets are entrained in the IRZ, increasing the heating rate of the particles and leading to the increased release of volatiles and char combustion. The flame becomes more compact and intense as swirl is increased to an optimum level, which is characterized in the EERC test facility as the point at which the flame makes contact with the burner quarl. Increasing swirl beyond this level can pull the flame into the burner region, unnecessarily exposing metal burner components to the intense heat of the flame and possible combustion in the coal pipe. Adjustments to the swirl setting were made manually by moving a lever arm attached to the movable block assembly. The position of the blocks was noted on a linear scale.

Increasing swirl to provide flame stability and increased carbon conversion can also affect the formation of NO_(x). The high flame temperatures and increased fuel-air mixing associated with increased swirl create an ideal situation under which NO_(x) may form. In full-scale burners with adjustable vanes, swirl is often increased to reach the optimum condition for carbon conversion, and then decreased slightly to reduce the production of NO_(x).

The general test method at the EERC facility sets the burner at its maximum level of swirl and monitors system parameters such as fuel feed rate, excess air, gaseous emissions such as O₂, CO₂, CO, SO₂, and NO_(x), combustor static, and air flow rates. Photographs of the flame and burner zone were taken through a sight port in the furnace just above the burner cone using standard 35-mm film. Flame temperature was also measured using a high-velocity thermocouple (HVT) at a set location in the furnace, and heat flux was monitored using a baseline heat-flux probe at the same location. An ash sample was collected at each swirl setting to establish carbon burnout. The swirl setting was then reduced until the flame was visually observed to lift off the burner quarl. At this point, the flame was characterized as unstable under full load conditions which are between 633 and 686 MJ/hr firing rate. Photographs were again taken to record the flame at this setting, temperature and heat flux measurements were taken, and an ash sample was taken once again. Once flame liftoff was established, the optimum swirl setting was located by visual observation of the flame, and measurements were recorded once again.

Flame stability under turndown conditions is characterized by firing the test fuel at a reduced load, typically one-half to three-quarters of the full load rate, maintaining the same primary air flow, and adjusting the secondary air flow to meet excess air requirements. The procedure described above was used to establish flame stability at reduced load.

The CTF utilizes two banks of Rosemount NGA gas analyzers to monitor O₂, CO, CO₂, and NO_(x). Sulfur dioxide (SO₂) is monitored by analyzers manufactured by Ametek. The analyzers are typically located at the furnace exit and the particulate control device exit. The gas analyses are reported on a dry basis. Baldwin Environmental manufactures the flue gas conditioners used to remove water vapor from each gas sample. The flue gas constituents are constantly monitored and recorded by the CTF's data acquisition system.

One of the probes used to characterize flame shape and intensity is the baseline heat-flux probe. The probe uses water to pick up heat from a 2.5 cm-thick stainless steel tip that is inserted into a port in the sidewall of the radiant zone so that its surface is flush with the inner wall of the combustion chamber. The water flow rate is measured by turbine flow meters and the temperature of the water is measured by Type K thermocouples in the inlet and exit water streams. Two thermocouples embedded in the outer and inner surface of the probe monitor metal temperatures. From these values the heat flux is calculated.

In addition to the baseline heat-flux probe, an HVT was used to measure the true gas temperature at the same location. The probe is water-cooled to protect its stainless steel outer shell from the intense heat of the combustion flame. A Type S thermocouple runs down its center and is shielded from the radiation of the flame and refractory walls by a tip made from insulation board. A vacuum pump is used to draw gases past the thermocouple junction at a rate sufficient to achieve a velocity past the thermocouple junction of 120 m/sec. At this velocity, the radiative component to heat transfer is minimized and convective heat transfer is dominant. In this manner, the true gas temperature can be obtained without the interference of radiation to or from the thermocouple junction.

Fly ash samples were obtained by various means at the inlet and outlet of the pilot plant ESP or BH. U.S. Environmental Protection Agency (EPA) Method 5 was used to establish particulate matter (PM) concentrations in the flue gas. High-volume sample extraction and the pilot plant control device collection hoppers can provide large samples for study.

Residual fuel oil samples were heated to lower the fuel viscosity prior to atomization in the burner. Fuel additives were added to the heated fuel stream near the atomizing nozzle by means of a specially designed metered injection system. In the injection system a fuel flow meter was used to ascertain fuel flow, the output was fed to a PID controller which then controlled the flow rate of a chemical metering pump. The concentration of the fuel additive was dynamically adjusted to any change in flow rate of the fuel. The output of the metering pump was injected into the flowing heated fuel producing a dispersion of droplets of the fuel additive in the fuel. This mixture then traversed a static mixing section which insured that the treated fuel was homogeneously mixed with the fuel before entering the atomizing section of the burner.

Tests were conducted for three days at the EERC facility with a furnace exit gas temperature (FEGT) between 1250° C. and 1315° C. and at an excess air level at or near 10%. This corresponds to approximately 2.0% oxygen in the flue gas at the furnace exit. The residual fuel oil firing rate and the combustion air flow rates were adjusted during each of these tests to maintain these levels. On the fourth day, each test performed at an FEGT between 1250° C. and 1315° C. and at an excess air level at or near 5%. Tables 2 through 7 provide baseline and run-average summaries of operating conditions for each test period during each day of testing. Control of the residual fuel oil feed rate was accomplished by adjusting the set point on the speed controller of the pump. The controller then adjusted pump speed to maintain the feed rate at the desired level. Excess air levels were achieved by manually adjusting valve positions on each of the primary and secondary air streams. A BH was used for particulate control during all test periods.

The furnace was preheated to 1290° C. with natural gas for up to 8 hours prior to the start of each day's testing. Furnace pressure was maintained near −1 torr by adjustment of a control valve blending ambient air into the duct at the inlet of the induced-draft fan.

Two banks of analyzers monitored gaseous emissions and were designated as furnace exit and BH exit in each of the following Tables 2 through 6. Furnace exit analyses were sampled approximately 1 meter downstream of the fouling probe bank. This oxygen level was used to control excess air levels during each test. BH exit analyses are normally obtained from the ductwork following BH. Because of the higher vacuum at the back end of the test system and the large number of flanged connections, air leakage into the ductwork resulted in a 1-2% increase in flue gas oxygen concentrations. The oxygen analysis from each bank of analyzers was used to correct gaseous emissions of interest to a constant excess air level of 20% (3.5% O₂). The calculation used to correct emissions levels reported here is:

${{Corrected}\mspace{14mu} S\; O_{2}},{{ppm} = \frac{\left\lbrack {{{Actual}\mspace{14mu} S\; O_{2}},{ppm}} \right\rbrack \times \left\lbrack {21 - {3.5\left( {{{Target}\mspace{14mu} O_{2}},\%} \right)}} \right\rbrack}{\left\lbrack {{21 - {{Actual}\mspace{14mu} O_{2}}},\%} \right\rbrack}}$

Gas analyzers were routinely zeroed and spanned prior to the start of each test. Additional calibration of the analyzers was performed when results were suspect or unexpected.

In Tests AF-CTS-751, 753, 755, 756-1, and 758 (twice), the primary objective was to establish baseline operating characteristics, emissions rates for the various gas species, and the work produced under the various operating conditions. In addition, fly ash samples were collected to determine the dust loading (or PM) of the gas stream entering the BH. Results from these tests are provided in Table 2 through 6. Once stable combustion conditions had been achieved after switching from natural gas to residual fuel oil, a series of measurements were made using an HVT, a baseline heat-flux probe, and a small cyclone to obtain fly ash samples. The swirl setting on the secondary air stream was held constant at 3.5 for all test periods performed during this test series.

In all other tests, the primary objective was to establish the effectiveness of various fuel additives for lowering regulated gaseous emissions and increasing the work produced. The same test protocol was used here to determine the effectiveness of the fuel additives. Results from these tests are provided in Tables 2 through 7. As part of the test protocol, a period of baseline operation typically preceded all test periods where a fuel additive was evaluated.

Following are the fuel additive formulations used in this study:

Additive 2: 5 mL meadowfoam oil (d=0.91 g/mL); 5.1 g fescue extract (hexane extracted); and 995 mL AROMATICS 150 FLUID (d=0.90 g/mL); not prepared in a glove box;

Additive 5: 5 mL meadowfoam oil (d=0.91 g/mL); 5.2 g alfeque extract (hexane extracted); 2 mL 2,2,4-trimethyl-6-ethoxy-1,2-dihydroquinoline (d=1.03); 1.6 g ISOMIXTENE®; and 993 mL AROMATIC 100 FLUID (d=0.87 g/mL); prepared in a glove box under non-oxygenation conditions;

Additive 6: 80% (v/v) Component 1 and 20% (v/v) Component 2 where: Component 1: 5 mL meadowfoam oil (d=0.91 g/mL); 5.1 g alfeque extract (hexane extracted); and 995 mL AROMATICS 150 FLUID (d=0.90 g/mL); not prepared in a glove box; Component 2: 2-ethylhexyl nitrate.

Additive 7: 80% (v/v) Additive 5 and 20% (v/v) 2-ethylhexyl nitrate.

Additive 8: 0.5 mL 2,2,4-trimethyl-6-ethoxy-1,2-dihydroquinoline (d=1.03); 0.8 g ISOMIXTENE®; 2.5 mL meadowfoam oil (d=0.91); 0.39 g fescue extract (hexane extracted); and 500 mL AROMATIC 100 FLUID (d=0.87); prepared in a glove box under non-oxygenation conditions.

Additive 9: 0.5 mL 2,2,4-trimethyl-6-ethoxy-1,2-dihydroquinoline (d=1.03); 0.8 g ISOMIXTENE®; 2.5 mL meadowfoam oil (d=0.91); 0.39 g alfeque extract (ethanol extracted); and 500 mL AROMATIC 100 FLUID (d=0.87); prepared in a glove box under non-oxygenation conditions.

Additive 10: 0.5 mL 2,2,4-trimethyl-6-ethoxy-1,2-dihydroquinoline (d=1.03); 0.8 g ISOMIXTENE®; 2.5 mL meadowfoam oil (d=0.91); 0.39 g alfeque extract (hexane extracted); and 500 mL AROMATIC 100 FLUID (d=0.87); prepared in a glove box under non-oxygenation conditions.

The following tables provide testing results for residual fuel oils and the listed fuel additives.

TABLE 2 Baseline and Test Run-Average Operating Parameters - AF-CTS-745 Test Number AF-CTS-745 AF-CTS-745 AF-CTS-745 Description Residual Fuel Oil Residual Fuel Oil Residual Fuel Oil Day 1 1 1 Test Period 1 2 3 Time 11:13-12:13 16:26-17:26 17:36-17:58 Swirl Setting 3.5 3.5 3.5 Fuel Feed Rate, kg/hr 16.6 15.9 15.6 Firing Rate, MJ/hr 728.77 705.00 691.54 Additive None Additive 2 Additive 2 Addition Rate, mL/hr N/A 30 60 Furnace BH Furnace BH Furnace BH Flue Gas Analysis Exit Exit Exit Exit Exit Exit O₂, % 2.19 3.22 2.06 3.02 1.92 2.77 CO₂, % 14.23 13.14 14.13 12.88 14.19 12.79 SO₂, ppm 1716 1687 1717 1681 1707 1678 NO_(x), ppm 169 131 161 106 156 128 CO, ppm 4.20 12.03 4.58 11.98 4.56 12.18 Excess Air, % 11.11 10.38 9.61 Emissions at 3.5% O₂ SO₂, ppm 1733 1803 1722 1776 1700 1749 SO_(2.) g/MJ 5.90 6.13 5.86 6.05 5.80 5.97 NO_(x), ppm 171 140 162 112 155 133 System Temperatures, ° C. Forced Draft Fan Outlet 63.3 66.1 66.1 Primary Air 283 281 279 Secondary Air 341 341 340 FEGT 1286 1288 1282 BH Inlet 179 176 176 BH Outlet 146 144 144 Stack 82.8 95 93.3 Oil Feed 88.9 88.9 89.4 Heat Flux Probe Temperatures, ° C. HVT 1334 1353 1343 Surface Metal 1 982.7 957.8 948.9 Surface Metal 2 963.3 938.9 920.6 Back Metal 1 740.5 701.7 693.9 Back Metal 2 687.8 662.2 652.8 Water Out 25.9 29.4 29.9 Water In 18.7 20.7 20.6 Water Flow, l/min 3.37 2.99 2.97 Heat Flux, MJ/m²-hr 1011 1073 1154 Burner Quarl Deposit Found Yes Yes No

TABLE 3 Baseline and Test Run-Average Operating Parameters - AF-CTS-753 Test Number AF-CTS-753 AF-CTS-753 AF-CTS-753 Description Residual Fuel Oil Residual Fuel Oil Residual Fuel Oil Day 2 2 2 Test Period 4 5 6 Time 8:38-11.01 11:33-12:57 14:20-14:35 Swirl Setting 3.5 3.5 3.5 Fuel Feed Rate, kg/hr 17.5 17.0 15.4 Firing Rate, MJ/hr 775.70 752.45 681.34 Additive None Additive 5 Additive 5 Addition Rate mL/hr N/A 30 60 Furnace BH Furnace BH Furnace BH Flue Gas Analysis Exit Exit Exit Exit Exit Exit O₂, % 2.02 2.68 2.03 2.85 2.12 2.91 CO₂, % 14.47 13.37 14.33 13.57 14.24 13.49 SO₂, ppm 1688 1681 1737 1712 1714 1691 NO_(x), ppm 207 173 203 174 205 176 CO, ppm 4.57 16.11 3.98 15.25 3.84 15.53 Excess Air, % 10.61 10.22 10.72 Emissions at 3.5% O₂ SO₂, ppm 1702 1743 1740 1792 1725 1776 SO₂, g/MJ 6.05 6.53 6.30 6.55 6.26 6.51 NO_(x), ppm 207 179 203 182 206 185 System Temperatures, ° C. Forced Draft Fan Outlet 58.9 60.6 62.8 Primary Air 300 300 301 Secondary Air 341 341 341 FEGT 1275 1285 1292 BH Inlet 175 175 176 BH Outlet 143 143 143 Stack 83.9 88.3 90.6 Oil Feed 93.3 95 93.3 Heat Flux, Temperatures, ° C. HVT 1354 1366 N/A Surface Metal 1 981.7 955 N/A Surface Metal 2 978.9 947.8 N/A Back Metal 1 702.2 676.1 N/A Back Metal 2 688.9 640.6 N/A Water Out 29.6 30.1 N/A Water In 20.6 20.7 N/A Water Flow, l/min 3.01 2.91 N/A Heat Flux, MJ/m²-hr 1126 1129 N/A Method 5 Sample Taken No Yes No

TABLE 4 Baseline and Test Run-Average Operating Parameters - AF-CTS-753 (cont.) & 754 Test Number AF-CTS-753 AF-CTS-754 Description Oil Oil Day 2 2 Test Period 7 8 Time 14:35-15:06 15:37-16:53 Swirl Setting 43.5 3.5 Fuel Feed Rate, kg/hr 17.1 16.2 Firing Rate, MJ/hr 758.50 719.34 Additive Additive 5 Additive 6 Addition Rate, mL/hr 15 40 Furnace Baghouse Furnace Baghouse Flue Gas Analysis Exit Exit Exit Exit O₂, % 1.80 2.59 2.00 2.79 CO₂, % 14.49 13.74 14.38 13.55 SO₂, ppm 1750 1721 1717 1696 NO_(x), ppm 199 171 211 182 CO, ppm 4.18 15.90 4.20 15.80 Excess Air, % 8.96 10.0 Emissions at 2.0% O₂ SO₂, ppm 1732 1776 1717 1770 SO₂ g/MJ 6.28 6.51 6.19 6.49 NO_(x), ppm 197 176 190 211 System Temperatures, ° C. Forced Draft Fan Outlet 62.8 62.8 Primary Air 300 282 Secondary Air 341 340 FEGT 1293 1284 Baghouse Inlet 176 173 Baghouse Outlet 143 142 Stack 91.1 88.3 Oil Feed 91.7 91.7 Heat Flux Probe Temperatures, ° C. HVT N/A 1343 Surface Metal 1 N/A 972.2 Surface Metal 2 N/A 946.7 Back Metal 1 N/A 683.3 Back Metal 2 N/A 643.9 Water Out N/A 30.5 Water In, N/A 21.3 Water Flow, 1/min N/A 2.85 Heat Flux, MJ/m²-hr N/A 1086 Method 5 Sample Taken No No

TABLE 5 Baseline and Test Run-Average Operating Parameters - AF-CTS-755 Test Number AF-CTS-755 AF-CTS-755 AF-CTS-745 Description Oil Oil Oil Day 3 3 3 Test Period 9 10 11 Time 9:20-9:44 9:48-10:14 10:15-10:41 Swirl Setting 3.5 3.5 3.5 Fuel Feed Rate, kg/hr 17.2 16.5 16.9 Firing Rate, MJ/hr 761.88 730.94 746.65 Additive None Additive 7 Additive 7 Addition Rate, mL/hr N/A 40 80 Furnace BH Furnace BH Furnace BH Flue Gas Analysis Exit Exit Exit Exit Exit Exit O₂, % 1.80 2.78 1.95 2.94 1.90 2.92 CO₂, % 14.55 14.01 14.42 13.87 14.46 13.88 SO₂, ppm 1773 1707 1751 1696 1753 1693 NO_(x), ppm 182 167 185 170 185 168 CO, ppm 6.82 19.22 7.05 18.18 10.46 22.44 Excess Air, % 8.96 9.77 9.50 Emissions at 2.0% O₂ SO₂, ppm 1755 1780 1746 1784 1744 1779 SO_(2.) g/MJ 6.32 6.32 6.32 6.34 6.32 6.34 NO_(x), ppm 180 174 185 179 184 177 System Temperatures, ° C. Forced Draft Fan Outlet 61.1 61.7 62.2 Primary Air 284 283 283 Secondary Air 342 342 342 FEGT 1274 1273 1276 BH Inlet 178 177 177 BH Outlet 145 144 144 Stack 90 90.6 90.6 Oil Feed 93.9 93.3 93.3 Heat-flux Probe Temperatures, ° C. HVT 1288 1299 N/A Surface Metal 1 935 939.4 N/A Surface Metal 2 912 917.8 N/A Back Metal 1 655 662.8 N/A Back Metal 2 622.8 633.3 N/A Water Out 30.07 30.38 N/A Water In 21.41 21.59 N/A Water Flow, l/min 2.79 2.75 N/A Heat Flux, MJ/m²-hr 997.6 998.5 N/A Method 5 Sample Taken No No No

TABLE 6 Baseline and Test Run-Average Operating Parameters - AF-CTS-756 & 757 Test Number AF-CTS-756-1 AF-CTS-756-2 AF-CTS-747 Description Oil Oil Oil Day 4 4 4 Test Period 12 13 14 Time 9:19-11:00 11:02-12:26 13:19-15:14 Swirl Setting 3.5 3.5 3.5 Fuel Feed Rate, kg/hr 16.3 16.0 15.8 Firing Rate, MJ/hr 723.13 707.01 701.21 Additive None Additive 8 Additive 9 Addition Rate, mL/hr N/A 40 40 Furnace BH Furnace BH Furnace BH Flue Gas Analysis Exit Exit Exit Exit Exit Exit O₂, % 0.98 1.71 1.03 1.77 1.14 1.87 CO₂, % 15.22 14.48 15.19 14.42 15.07 14.35 SO₂, ppm 1796 1861 1867 1847 1845 1856 NO_(x), ppm 186 175 193 180 176 172 CO, ppm 43.0 65.0 12.5 22.4 10.3 18.8 Excess Air, % 4.68 4.94 5.49 Emissions at 2.0% O₂ SO₂, ppm 1794 1833 1776 1825 1765 1843 SO_(2.) g/MJ 6.14 6.68 6.38 6.66 6.36 6.72 NO_(x), ppm 177 172 184 178 168 171 System Temperatures, ° C. Forced Draft Fan Outlet 55 56.1 57.8 Primary Air 270 269 269 Secondary Air 338 338 338 FEGT 1287 1289 1286 BH Inlet 171 179 178 BH Outlet 138 144 144 Stack 72.8 77.2 81.1 Oil Feed 90.6 88.3 89.4 Heat-flux Probe Temperatures, ° C. HVT 1288 1290 1296 Surface Metal 1 961.7 967.8 955 Surface Metal 2 948.3 945 932 Back Metal 1 696.1 702.8 700.6 Back Metal 2 666.1 672.2 671.1 Water Out 29.42 29.93 30.44 Water In 20.19 20.79 22.11 Water Flow, l/min 2.66 2.61 2.46 Heat Flux, MJ/m²-hr 1020 983.4 848.4 Method 5 Sample Taken Yes Yes Yes

TABLE 7 Baseline and Test Run-Average Operating Parameters - AF-CTS-758 Test Number AF-CTS-758 AF-CTS-758 AF-CTS-748 Description Oil Oil Oil Day 4 4 4 Test Period 15 16 17 Time 15:27-15:48 15:48-17:06 17:06-17:34 Swirl Setting 3.5 3.5 3.5 Fuel Feed Rate, kg/hr 15.9 15.9 15.8 Firing Rate, MJ/hr 705.56 706.53 702.66 Additive None Additive 10 None Addition Rate, mL/hr N/A 40 N/A Furnace BH Furnace BH Furnace BH Flue Gas Analysis Exit Exit Exit Exit Exit Exit O₂, % 1.14 1.87 1.09 1.84 1.14 1.86 CO₂, % 15.09 14.45 15.11 14.38 15.07 14.35 SO₂, ppm 1844 1845 1844 1850 1837 1836 NO_(x), ppm 177 168 180 172 183 174 CO, ppm 11.7 21.6 11.8 22.0 8.6 18.3 Excess Air, % 5.49 5.24 5.49 Emissions at 2.0% O₂ SO₂, ppm 1764 1832 1760 1835 1757 1823 SO_(2.) g/MJ 6.34 6.64 6.34 6.68 6.32 6.64 NO_(x), ppm 169 167 172 171 175 173 System Temperatures, ° C. Forced Draft Fan Outlet 58.3 58.9 58.9 Primary Air 269 269 269 Secondary Air 338 338 338 FEGT 1289 1291 1290 BH Inlet 178 176 177 BH Outlet 145 144 144 Stack 85 85 85.6 Oil Feed 89.5 89.4 90 Heat-Flux Probe Temperatures, ° C. HVT N/A 1296 N/A Surface Metal 1 850 906.7 917.2 Surface Metal 2 840 868.3 875.6 Back Metal 1 571.7 606.1 632.8 Back Metal 2 551.1 585 592.2 Water Out 30.69 30.34 30.46 Water In 22.07 22.34 22.47 Water Flow, l/min 2.95 2.94 2.91 Heat Flux, MJ/m²-hr 1052 966.9 957.9 Method 5 Sample Taken No Yes No

Initial shakedown testing began the day before actual testing and included firing the baseline residual fuel oil to establish the effectiveness of changes that had been made to the system following the first series of fuel additive tests performed earlier. This shakedown period verified that the changes made improved the overall operability of the system. Included among the many changes made were the addition of insulation to various system feed lines, the piping of steam to the burner gun for use as the atomizing fluid for the oil, the addition of a mixing section in the fuel feed line, and the addition of steam heaters on the storage barrel that was used to fill the feed tank so as to maintain a residual fuel oil temperature at or near 240° F. The result of the changes allowed the fuel to be fed continuously through the burner gun with no carbon deposits forming on the gun or the air piping within the burner quarl.

The FEGT was maintained near 2350° F. for all test periods. In some cases, it was allowed to rise to see the effect of the fuel additive on the work produced, and in other cases, it was maintained during fuel additive injection to determine the level of fuel savings achieved while maintaining the same level of work produced. Because the changes in fuel and operating parameters provided a very stable combustion environment, the combustion efficiency was very high for all test periods. This made it difficult to monitor changes in the combustion environment resulting from fuel additive addition. Changes in the combustion environment were noted, though, during this period and are detailed below. Because of the difficulty of monitoring changes, the excess air level was lowered to approximately 5% during the final day of testing on Day 4.

Two banks of analyzers, one at the furnace exit and one at the BH outlet, were used to determine the concentration of the combustion products in the gas stream. Measurements of flue gas O₂, CO, CO₂, SO₂, and NO_(x) were continuously monitored and recorded by the CTF data acquisition system. Test period averages have been provided in Tables 2 through 7.

Excess air levels fluctuated with changes in the fuel feed rate and varied from around 9% to 11% during the tests conducted from June 21 through June 23. Corrected SO₂ emissions were fairly steady at an average of approximately 1720 ppm±20 ppm for all test periods near 10% excess air.

An analysis of the data indicates that each of the analytical observables is a strong function of the excess air. When a spline fit is drawn through the data points, one gets a much better comparison view than if the data is globally fit. Furnace and baghouse data are treated separately. Looking at the NO_(x) and CO data for both the furnace and the baghouse (FIGS. 7 and 8, respectively), one finds that the results for one of the treated runs are consistently lower than those of the baseline measurements at equal excess air. Additive 2 shows a consistent improvement in gaseous emissions. Surprisingly, this fuel additive shows its effect even though it was only used in experiments with excess air of about 10%.

Particulate Matter (PM) emission values measured and expressed as dust loadings were obtained at the BH inlet during a number of test periods using U.S. Environmental Protection Agency Method 5 PM sampling. Such testing provided significant evidence of the effectiveness of various fuel additives in improving the combustion characteristics of the residual fuel oil (see FIG. 9). During the baseline test on Day 4 (Test Period 12), the dust loading entering the BH was determined to be 0.122 g/m³. During Test Period 5, Additive 5 was injected at a rate of 30 mL/hr where EPA Method 5 dust loading was significantly reduced to 0.0677 g/m³, a 44.6% reduction. In Test Period 13, Additive 8 was utilized at an addition rate of 40 mL/hr as was Additive 10 in Test Period 16. EPA Method 5 dust loading was reduced during the use of Additive 8 to 0.0886 g/m³ and to 0.0959 g/m³ during the use of Additive 10. This translates to a 27.5% reduction and a 21.5% reduction, respectively. It should be noted that the excess air levels during Test Period 5 (Additive 5) were higher than they were for Test Period 12, the baseline test period, so a portion of the reduction noted here can be accounted for by the increase in available oxygen. However, this was not the case for Test Periods 13 (Additive 8) and 16 (Additive 10). Excess air levels were approximately the same during the baseline test period as they were for the two noted testing periods.

While heat flux behavior is a complicated function, it is assumed to be a function of at least the fuel firing rate and the excess air. FIG. 10 plots the heat flux as measured at EERC divided by the fuel firing rate versus excess air reported. The data demonstrates that the heat flux/fuel ratio produced for fuel treated with Additive 2 was greater than that seen for the untreated fuel. An improvement of from 7.6% to 10.1% in heat flux ratio was seen for Additive 2.

An infrared (IR) camera/recorder was used to evaluate any changes in flame temperature that might occur between periods of baseline operation and fuel additive injection. Results from these measurements have been summarized in Table 8. It would appear from the data below that the most telling trend in flame temperature was the oil feed rate. This relationship can be seen in FIG. 6. The equation of the linear regression line has been provided and the R² value calculated. The flame temperature does not fit a linear relationship with feed rate well, but does trend in that direction. Although the test furnace was operated at a similar furnace exit gas temperature during each day of operation, the corresponding flame temperature varies significantly from day to day, as does the feed rate required to achieve that temperature. This indicates that the heat flux through the furnace walls tends to change from day to day. However, within a single day's operation only small trends may be noted.

During the first day of testing, the recorded flame temperature just prior to fuel additive injection and immediately following injection of Additive 2 remained constant at 1333° C. The feed rate was also constant. However, during the second day of testing, the baseline feed rate (Test Period 4) was considerably higher than during fuel additive injection. Flame temperature readings from the IR camera were constant at 1402° C. during Test Periods 5 and 7 with the injection of Additive 5 at the 30 mL/hr and 15 mL/hr rate, respectively. This would indicate some effect of the fuel additive on heat release in the furnace. During Test Period 8, Additive 6 was injected at the 40 mL/hr rate. While the flame temperature decreased to 1392° C., the feed rate was significantly reduced from baseline levels during this period to 16.23 kg/hr.

TABLE 8 Summary of IR Camera Recorder Data Injection Oil Feed Test Rate, Rate, IR Flame Period Day Additive (mL/hr) (kg/hr) Temp. (° C.) 1 Day 1 None None 15.02 1333 2 Day 1 Additive 2 30 15.91 1333 4 Day 2 None None 17.50 1402 5 Day 2 Additive 5 30 16.98 1402 7 Day 2 Additive 5 15 17.12 1402 8 Day 2 Additive 6 40 16.23 1392 9 Day 3 None None 17.19 1366 10 Day 3 Additive 7 40 16.50 1366 12 Day 4 None None 16.32 1371 13 Day 4 Additive 8 40 15.95 1359 14 Day 4 Additive 9 40 15.82 1359 15 Day 4 None None 15.92 1362 16 Day 4 Additive 10 40 15.94 1360

The baseline flame temperature of 1366° C. was achieved in Test Period 9 with a feed rate of 17.19 kg/hr of residual fuel oil. After the injection of Additive 7 at the 40 mL/hr rate, the flame temperature remained constant at a lower feed rate of 16.50 kg/hr. This represents a reduction in feed of approximately 4%. During the final day of testing, the initial baseline flame temperature was recorded at 1371° C. (Test Period 12). Although the temperature dropped to 1359° C. during the injection of Additives 8 and 9, it remained relatively constant throughout the day, rising to 1362° C. during the baseline Test Period 15 that followed. Essentially no change occurred during Test Period 16 when injecting Additive 10 at the 40 mL/hr rate. The flame temperature held constant at 1360° C.

CANMET Research Furnace Testing

Testing was also conducted at the CANMET Research Furnace in Ottawa, Canada. The residual fuel oil used in the tests was obtained from PROVMAR Fuels Inc. of Hamilton, Ontario. The properties for the residual fuel oil are listed in Table 9. Such residual fuel oil has a moderate sulfur content of about 1.7%, with a very high heating value of 42.12 MJ/kg at a moisture content of 0.05%. The proximate, ultimate, and heating value analyses for the residual fuel oil tested are also provided in Table 1 along with the theoretical emission limit of sulfur.

TABLE 9 Grade ISO 8217:05 RMG380 Property Result Specification Test Method Density, kg/m3 @ 15° C. 1021.3 991.0 Max ISO 12185 Viscosity cst @ 50° C. 513.5 380.0 Max ISO 3104 Viscosity cst @ 80° C. 94.4 Max ISO 3104 Flash Point, ° C. 110°  60.0° Min ISO 2719 Pour Point, ° C.  0°    30° Max ISO 3016 MCR, % m/m 13.92 18.00 Max ISO 10370 Ash, % m/m 0.066 0.150 Max ISO 6245 Water, % v/v 0.05  0.50 Max ISO 3733 Sulfur, % m/m 1.73  4.50 Max ISO 8754 Compatibility, Spot# 1    2 Max ASTM 474 Vanadium, mg/kg 107   300 Max ASTM D5863 Sodium, mg/kg 14 Max ASTM D5863 Silicon, mg/kg 34 Max ISO 10478 Aluminum, mg/kg 39 Max ISO 10478 Al & Si, mg/kg 73   80 Max CALC. Fe, mg/kg: 13.4 Max ASTM D5863 Pb, mg/kg: 0 Max ASTM D5863 Zn, mg/kg: 0 Max ASTM D5863 Mg, mg/kg: 0 Max ASTM D5863 Ca, mg/kg: 2 Max ASTM D5863 Ni, mg/kg: 25.6 Max ASTM D5863 K, mg/kg: 2.3 Max ASTM D5863 Total Sed, Pot., % m/m 0.04  0.10 Max ISO 10307-2 Asphaltenes, % m/m: 7.1 ASTM D3279 CCAI, Index# 879   860 Net Cal, Val, MJ/Kg (ASTM D4868) 42.12 Gross Heating Value (ASTM D4868) BTU/lb 18109 BTU/Gal 154122 Injection Temp 10 cst, ° C. 151 Injection Temp 15 cst, ° C. 134 Min Pump Temp 1,000 cst, ° C. 41 Ultimate Analysis (ASTM5291) C, % weight 87.79 H, % weight 10.4 N, % weight 0.38

The residual fuel oil was stored cold prior to testing. A day tank was used to heat the residual fuel oil to 121° C. and to keep the fuel hot during testing.

In this test protocol the furnace control was primarily based on the fuel flow into the furnace. The fuel flow was held constant along with the air flow. A calorimetric section of the furnace allowed one to determine the heat transfer from the furnace as a function of distance from the burner. There was no “baghouse” in this system and the furnace exit temperature was allowed to float.

When firing a liquid fuel such as residual fuel oil, a pump is used to convey the fuel through a dual-fluid atomizer into the combustion chamber. In this furnace, compressed air is used as the atomizing fluid. Combustion air is preheated by an electric air heater.

Flame stability is assessed by observation of the flame via a quartz observation port located along the longitudinal axis of the furnace at the furnace end opposite the burner. Under normal operation a video camera was used to qualitatively assess the flame quality and to create a video record of the flame characteristics occurring during an experiment.

The general test method sets the burner at its maximum level of swirl and monitors system parameters such as fuel feed rate, excess air, gaseous emissions (O₂, CO₂, CO, SO₂, and NO_(x)), combustor static, and air flow rates. Photographs of the flame and burner zone are then taken through a sight port in the furnace just above the burner cone using a video camera.

The CANMET furnace uses two banks of gas analyzers to monitor O₂, CO, CO₂, and NO_(x). Sulfur dioxide (SO₂) is also monitored. The analyzers are typically located at the furnace exit and the particulate control device exit. The gas analyses are reported on a dry basis. The flue gas constituents are monitored and recorded by the data acquisition system at 10 second intervals during the experiment. Statistical characteristics of the measured quantities were used to establish confidence limits on the measured data.

In the calorimetric section of the furnace, inlet and exit temperatures are monitored at 10 second intervals and recorded by the data acquisition system. The flow rates of the therminol working fluid are also measured and accessible via the data acquisition system. From these measurements the heat transfer in the furnace can be determined as a function of time for each of the 28 calorimetric bands along the long axis of the furnace.

Ash samples were obtained by various means at the inlet and outlet of the pilot plant ESP or BH. Isokinetic gas sampling is used to establish particulate matter (PM) concentrations in the flue gas. High volume sample extraction and the pilot plant control device collection hoppers can provide large samples for study. Chemical composition was also determined for the collected ash samples. Collection of the isokinetic dust samples required approximately 3 hrs per sample. There was only one ash sample collected per run.

The residual fuel oil was heated to lower its viscosity prior to atomization in the burner. Fuel additives were added to the heated fuel stream near the atomizing nozzle by means of a specially designed metered injection system. In the injection system a fuel flow meter was used to ascertain fuel flow, the output was fed to a PID controller which controlled the flow rate of a chemical metering pump. The concentration of the fuel additive was dynamically adjusted to any change in flow rate of the fuel. The output of the metering pump was injected into the flowing hot fuel producing a dispersion of droplets of the fuel additive in the warm fuel. This mixture then traversed a static mixing section to homogeneously mix the fuel additive with the fuel before entering the atomizing section of the burner.

Tests performed at the CANMET research furnace were performed with furnace operation specified by fuel flow rate and excess air level, both of which were controlled by the furnace operator. The furnace was preheated with natural gas for up to 5 hrs prior to beginning experiments on residual fuel oil. Standard start up protocol involved collection of data with untreated fuel oil burning in the system for at least one hour prior to beginning any experimental treatment. This protocol enabled one to verify baseline behavior on each day of operation. The experiments were designed to investigate the effects of the chemical additives on furnace operation at two different excess air concentrations (10% and 7.5%). Baseline operation of the fuels was determined at the beginning and end of test campaigns as well as at the start of each test day.

In the testing, all of the fuel additives were evaluated at the 10% excess air level, and only the best performers were evaluated at the lowered excess air level. The fuel additive compositions for the CANMET testing were prepared as follows with additives containing ISOMIXTENE® (Additives 13 and 14) prepared under inert atmosphere in a glove box, and additives without ISOMIXTENE® (Additives 11, 12, 15, and 16) prepared under normal atmospheric conditions:

Additive 11 was prepared by mixing 13.9 grams of fescue extract and 10 mL of meadowfoam oil, and then blending the mixture with AROMATIC 150 FLUID up to 2000 mL.

Additive 12 was prepared by mixing 13 grams of fescue extract, 10 mL of meadowfoam oil and 1 mL of SANTOQUIN®, and blending the mixture with AROMATIC 150 FLUID up to 2000 mL.

Additive 13 was prepared by mixing 5.12 grams of fescue extract, 5 mL of meadowfoam oil, 10 drops of SANTOQUIN®, and 0889 grams of ISOMIXTENE®, and blending the mixture with AROMATIC 150 FLUID up to 1000 mL.

Additive 14 was prepared by mixing 5.13 grams of alfalfa extract, 5 mL of meadowfoam oil, 10 drops of SANTOQUIN®, and 088 grams of ISOMIXTENE®, and blending the mixture with AROMATIC 150 FLUID up to 1000 mL.

Additive 15 was prepared by mixing 13 grams of alfalfa extract, 10 mL of meadowfoam oil, and 2 mL of SANTOQUIN®, and blending the mixture with AROMATIC 150 FLUID up to 2000 mL.

Additive 16 was prepared by mixing 13 grams of alfalfa extract, and 10 mL of meadowfoam oil, and blending the mixture with AROMATIC 150 FLUID up to 2000 mL.

Table 10 summarizes the observations for particulate matter concentration in the CANMET tests performed at 10% excess air. The carbon content of the ash collected from the treated fuel experiments were uniformly lower than that seen in the reference system, but the overall isokinetic dust loading showed modest increases for Additives 11 and 12. At a lower excess air ratio the carbon content of the collected ash was consistent with the isokinetic dust loading as shown in Table 11. Additive 15 showed consistent reduction in particulate loading.

TABLE 10 CANMET Testing: Particulate Matter Concentration at 10% Excess Air level Isokinetic Dust Ash Carbon Content Carbon Test Run Loading (mg/m³) (% Carbon) Reduction (%) Reference 129 79.9% — Additive 11 150 77.5% −13% Additive 12 144   78% −9% Additive 13 119 71.1% 18% Additive 14 119 72.7% 16% Additive 15 105 74.7% 24% Additive 16 124 75.7% 9%

TABLE 11 Dust Loading Results 7.5% Excess Air. Isokinetic Dust Ash Carbon Content Carbon Reduction Test Run Loading (mg/m³) (% Carbon) (%) Reference 208 75.4 — Additive 12 134 66.9 42.8 Additive 14 232 79.2 −17.0 Additive 15 160 67.6 31.0 Additive 16 200 78.4 0

Qualitatively, the flames for several of the treated fuels appeared shorter and brighter than the flames observed for the reference (untreated) fuels. This observation is supported by the flame video, but is difficult to quantify. A shorter more dense flame should provide maximum heat transfer in the calorimetric section of the furnace. Data supporting this is found in Tables 12 and 13 for experiments performed at both 10% and 7.5% excess air. Data was collected every 10 seconds to build a large statistical sample. The standard deviation of this data set provides an estimate of uncertainty. The measured therminol heat uncertainty is about 1%. The measured flue gas heat uncertainty is about 0.1%. Heat Disposition changes above 2% are statistically significant at the 95% confidence level

TABLE 12 Heat Disposition from Available Heat at 10% Excess Air Heat to Lost Heat Test Run Therminol Heat to Flue Gas “Lost Heat” Reduction Reference 62.7% 8.8% 28.5% — Additive 11 65.9% 9.2% 24.9% 3.6% Additive 12 65.9% 9.0% 25.1% 3.4% Additive 13 64.9% 8.8% 26.3% 2.2% Additive 14 67.3% 8.9% 23.8% 4.7% Additive 15 64.1% 9.1% 26.8% 1.7% Additive 16 66.2% 9.2% 24.6% 3.9%

TABLE 13 Heat Disposition from available Energy at 7.5% Excess Air Heat to Lost Heat Test Run Therminol Heat to Flue Gas “Lost Heat” Reduction Reference 62.7% 9.16% 28.1% — Additive 12 64.1% 9.67% 26.2% 1.9% Additive 14 65.6% 9.45% 24.9% 3.2% Additive 15 63.8% 9.37% 26.8% 1.3% Additive 16 65.4% 9.41% 25.2% 2.9%

IPT Laboratory Testing

Testing was also run at the IPT Laboratory Test Facility in Sao Paulo, Brazil. The IPT test furnace is operated similarly to that at CANMET. The IPT test facility employs a horizontal burner, Model MPR, manufactured by ATA Combustao Tecnica of Brazil that is fitted with an external water-cooled jacket. The fuel charge rate and excess air of the flue gas are taken as independent variables and the other observables are treated as dependent variables. The furnace contains a calorimetric section. One significant difference in the experiments performed in Brazil is related to the fuel. Brazilian fuel specifications are significantly different than those adopted in the United States. For example, the density and asphaltene content of the residual fuels commonly used in Brazil are significantly greater than those commonly used in the United States. At these very high asphaltene and viscosity levels, pollution caused by unburned carbon (particulate matter) is of primary importance. Part of the strategy to minimize this problem involves combusting the fuel under very high excess oxygen conditions. Standard operating procedure in Brazil calls for operating a furnace at furnace exit oxygen content of about 7% or about 37.5% excess air.

The fuel additive evaluated at IPT contained a combination of plant extract and an organometallic iron complex. In particular, 49.2 grams of alfalfa extract were mixed with 7.57 mL of SANTOQUIN® antioxidant, and 37.9 mL of meadowfoam oil. The mixture was combined with AROMATIC 150 FLUID up to 3785 mL, and 600 mL of the resulting mixture was further mixed with 117 grams of iron naphthenate and 190 mL of iron pentacarbonyl. This formulation was prepared under normal atmospheric conditions with the iron naphthenate transferred anaerobically using a syringe. The iron content of the resulting solution was 6 wt. %. The residual fuel oil tested at IPT was additized with this additive at 813 ppm.

Table 14 shows particulate matter concentrations observed under treated and untreated conditions. The reduction in particulate matter is very significant at both 4.5% and 7% oxygen levels, but perhaps the more significant observation is that the particulate matter concentration observed under treated conditions for both the oxygen concentrations are very close. It is well known that under high excess oxygen combustion conditions, a significant fraction of the heat is lost to the flue gas. The tests showed that by shifting from 7.0% excess oxygen to about 4.5% excess oxygen, a 17% improvement in useful heat was realized. Using the fuel additive tested, this increase in efficiency was accompanied by a 43% decrease in particulate matter emissions.

TABLE 14 Particulate Emission at IPT Brazil Particulate Concentration Excess O Additive Trial Number (mg/Nm3) 7.0% none 31 272 7.0% none 32 301 7.0% none 33 291 7.0% none 42 289 7.0% none 43 296 7.0% yes average 290 7.0% yes 34 183 7.0% yes 35 200 7.0% yes 36 128 7.0% yes 37 152 7.0% yes 38 128 7.0% yes 39 133 7.0% yes 40 111 7.0% yes 41 128 7.0% yes average 145 4.5% none 57 415 4.5% none 58 389 4.5% none 59 415 4.5% none 67 479 4.5% none 68 504 4.5% none 69 523 4.5% none average 454 4.5% yes 60 163 4.5% yes 61 166 4.5% yes 62 160 4.5% yes 63 162 4.5% yes 65 173 4.5% yes 66 169 4.5% yes average 166

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. 

1. A fuel additive for improving the combustion characteristics of a high-asphaltene carbonaceous fuel, the fuel additive comprising: a plant extract; and an organometallic compound.
 2. The fuel additive of claim 1 wherein the plant extract is an extract of a plant from the Leguminosae family.
 3. The fuel additive of claim 2 wherein the plant extract is selected from the group consisting of fescue extract, alfeque extract, alfalfa extract, and combinations thereof.
 4. The fuel additive of claim 3 wherein the organometallic compound is a hydrocarbon-soluble organometallic compound containing at least one metal selected from the first and second row transition metals.
 5. The fuel additive of claim 4 wherein the metal of the organometallic compound is iron
 6. The fuel additive of claim 5 wherein the organometallic compound is selected from the group consisting of iron pentacarbonyl, iron naphthenate, ferrocene, and combinations thereof.
 7. The fuel additive of claim 1 wherein the organometallic compound is a hydrocarbon-soluble organometallic compound containing at least one metal selected from the first and second row transition metals.
 8. The fuel additive of claim 7 wherein the metal of the organometallic compound is iron
 9. The fuel additive of claim 8 wherein the organometallic compound is selected from the group consisting of iron pentacarbonyl, iron naphthenate, ferrocene, and combinations thereof.
 10. The fuel additive of claim 1 further comprising an oil-soluble carrier.
 11. The fuel additive of claim 10 wherein the oil-soluble carrier is an aromatic solvent.
 12. The fuel additive of claim 10 wherein the plant extract is provided in an amount from about 0.01 wt. % to about 10 wt. % of the fuel additive.
 13. The fuel additive of claim 12 wherein the plant extract is provided in an amount from about 0.05 wt. % to about 5 wt. % of the fuel additive.
 14. The fuel additive of claim 13 wherein the plant extract is provided in an amount of about 0.5 wt. % of the fuel additive.
 15. The fuel additive of claim 1 further comprising a material selected from meadowfoam oil, a carotenoid, an anti-oxidant, and combinations thereof.
 16. The fuel additive of claim 1 further comprising meadowfoam oil, a carotenoid, and an anti-oxidant.
 17. The fuel additive of claim 16 wherein the carotenoid comprises β-carotene.
 18. The fuel additive of claim 16 wherein the anti-oxidant comprises a dihydroquinoline.
 19. The fuel additive of claim 18 wherein the dihydroquinoline comprises 2,2,4-trimethyl-6-ethoxy-1,2-dihydroquinoline.
 20. The fuel additive of claim 1 wherein the plant extract is extracted by a hydrocarbon-soluble polar or nonpolar solvent.
 21. A method of improving the combustion characteristics of a high-asphaltene carbonaceous fuel comprising adding a fuel additive to the high-asphaltene carbonaceous fuel, the fuel additive comprising: a plant extract; and an organometallic compound.
 22. The method of claim 21 wherein the plant extract is an extract of a plant from the Leguminosae family.
 23. The method of claim 22 wherein the plant extract is selected from the group consisting of fescue extract, alfeque extract, alfalfa extract, and combinations thereof.
 24. The method of claim 23 wherein the organometallic compound is a hydrocarbon-soluble organometallic compound with a metal selected from the first and second row transition metals.
 25. The method of claim 24 wherein the metal of the organometallic compound is iron.
 26. The method of claim 25 wherein the organometallic compound is selected from the group consisting of iron pentacarbonyl, iron naphthenate, ferrocene, and combinations thereof.
 27. The method of claim 21 wherein the organometallic compound is a hydrocarbon-soluble organometallic compound with a metal selected from the first and second row transition metals.
 28. The method of claim 27 wherein the metal of the organometallic compound is iron.
 29. The method of claim 28 wherein the organometallic compound is selected from the group consisting of iron pentacarbonyl, iron naphthenate, ferrocene, and combinations thereof.
 30. The method of claim 21 wherein the fuel additive further comprises an oil-soluble carrier.
 31. The method of claim 21 wherein the oil-soluble carrier is an aromatic solvent.
 32. The method of claim 21 wherein the high-asphaltene carbonaceous fuel is selected from residual fuel oil and coal.
 33. The method of claim 32 wherein the plant extract is provided in an amount from about 0.5 ppm to about 10,000 ppm of the amount of high-asphaltene carbonaceous fuel.
 34. The method of claim 33 wherein the plant extract is provided in an amount from about 200 ppm to about 2000 ppm of the amount of high-asphaltene carbonaceous fuel.
 35. The method of claim 34 wherein the plant extract is provided in an amount of about 800 ppm of the amount of high-asphaltene carbonaceous fuel.
 36. The method of claim 21 wherein the fuel additive further comprises a material selected from meadowfoam oil, a carotenoid, an anti-oxidant, and combinations thereof.
 37. The method of claim 21 wherein the fuel additive further comprises meadowfoam oil, a carotenoid, and an anti-oxidant.
 38. The method of claim 37 wherein the carotenoid comprises β-carotene.
 39. The method of claim 37 wherein the anti-oxidant comprises a dihydroquinoline.
 40. The method of claim 39 wherein the dihydroquinoline comprises 2,2,4-trimethyl-6-ethoxy-1,2-dihydroquinoline.
 41. The method of claim 21 wherein the plant extract is extracted by a hydrocarbon-soluble polar or nonpolar solvent.
 42. A fuel comprising a high-asphaltene carbonaceous fuel and a fuel additive, the fuel additive comprising: a plant extract; and an organometallic compound.
 43. The fuel of claim 42 wherein the plant extract is an extract of a plant from the Leguminosae family.
 44. The fuel of claim 43 wherein the plant extract is selected from the group consisting of fescue extract, alfeque extract, alfalfa extract, and combinations thereof.
 45. The fuel of claim 42 wherein the organometallic compound is a hydrocarbon-soluble organometallic compound with a metal selected from the first and second row transition metals.
 46. The fuel of claim 45 wherein the organometallic compound is selected from the group consisting of iron pentacarbonyl, iron naphthenate, ferrocene, and combinations thereof.
 47. The fuel of claim 42 wherein high-asphaltene carbonaceous fuel is selected from residual fuel oil and coal.
 48. The fuel of claim 47 wherein the plant extract is provided in an amount from about 0.5 ppm to about 10,000 ppm of the high-asphaltene carbonaceous fuel.
 49. The fuel of claim 48 wherein the plant extract is provided in an amount from about 200 ppm to about 2000 ppm of the high-asphaltene carbonaceous fuel.
 50. The fuel of claim 49 wherein the plant extract is provided in an amount of about 800 ppm of the high-asphaltene carbonaceous fuel
 51. The fuel of claim 42 further comprising a material selected from meadowfoam oil, a carotenoid, an anti-oxidant, and combinations thereof
 52. The fuel of claim 42 further comprising meadowfoam oil, a carotenoid, and an anti-oxidant.
 53. The fuel of claim 52 wherein the carotenoid comprises β-carotene.
 54. The fuel of claim 52 wherein the anti-oxidant comprises a dihydroquinoline.
 55. The fuel of claim 54 wherein the dihydroquinoline comprises 2,2,4-trimethyl-6-ethoxy-1,2-dihydroquinoline.
 56. The fuel of claim 42 wherein the plant extract is extracted by a hydrocarbon-soluble polar or nonpolar solvent. 